Motor vehicle



sept. 2, 41941, M Q, LEY l 2,254,491 Y MOTOR VEHICLE (imam/kw M.` OLLEYMOTOR VEHICLE Sept. 2, 1941.

2 Sheets-Sheet- 2V Filed Aug. 2, 1933 Patented Sept. 2, 17941 2,254,491l l Moron vaincu:

Maurice Olley, Pleasant Ridge, Mich., assignor to General MotorsCorporation, Detroit, Mich., a

corporation of Delaware Application August 2, 1933, Serial No. 683,239

1 Claim.

' ingly high speeds over the highways and while the vehicle itself iscapable of sustaining these high speeds, the actual riding comfort andthe ease of handling leave much to be desired. The

occupants are fatigued by the oscillations or what l may be termed theaction of the car with effects which are accentuated as the speedincreases.

The conventional automobile has its framework together with itsnecessary mechanical parts so arranged and organized as to provideqabody space thereon and the whole is then suspended on the wheels.Efforts to improve the riding comfort or ride and the ease of handlingor stability on the road, or roadability, have been largely directed tothe suspension and almost entirely to the springs, their mountings, andmeans to modify the action of the springs.

The road shocks at the wheels of a motor vehicle acting through thesprings, front and rear, result in oscillating motions of the vehiclebody. The shocks may take place in any conceivable combination, underany or all of the lroad wheels separately or together but, as measuredin a vertical longitudinal plane, (and it is the motion in (such a planewith which this invention is concerned) the oscillations separately,simultaneously, or in any phase relationship always take place about twovirtual but none the less definitely xed transverse axes for any givenvehicle and condition of loading. 1

While it has been appreciated heretofore that the oscillations were ofthe foregoing nature, the Y importance from the standpoint of ride ofthe frequencies of these oscillations and the particular location of theaxes of oscillation relative to the motor vehicle and to one anotherhasl not been fullyunderstood.

It is a common experience to find that a given automobile will, undercertain# and usually abnormal load conditions, have improved ride androadability, but, no automobile has heretofore been built in which theoptimum value of all the considerations affecting ride and readability,l. e. the distribution of the sprung masses, the position of the centerof gravity, the ratio of the spring deflection front and rear, and theactual frequency of the oscillations, has been realized.

The general object of the invention is an automobile of improved ridingcomfort and road stability.

It is a specific object of the invention to enl sure that the principaloscillations of the automobilebody as a result of road shocks are ofsubstantially equal frequency about determinate transverse axes.

It is a further object of the invention to secure theaforementioned'objects with the best possible relationship between theprincipal factors controlling ride and vroadability" which are theposition of the center of gravity, the actual-and relative springdeflection of the front and rear end of the automobile, land thedistribution of the sprung masses, which factors are interdependent, andto some extent, conflicting in .their influence.

The above and other objects of the invention are achieved by arrangingand disposing the essential parts and constituents of the sprung mass ofthe automobile so as in themselves to provide the best longitudinaldistribution of the suspended masses relatively to the road wheel axesand then providing a suitable spring suspension so that the vehicle bodywill oscillate as closely as possible vertically up and down withcombined oscillations of a comfortable frequency giving a so-calledfflat ride," free from violent pitching.

Experiment and experlencehave shown that the ride of the car or the'comfort of the passengers requires that the periodicity of oscillationsof any kind and from any source should be within the range of to 90cycles per minute. Any other frequencies are liable to cause fatigue anddiscomfort.

'I'he natural period or frequency of oscillation of 'a spring supportedmass is a function of the spring deflection, which is measured as theamount by which the spring is compressed from a free to a fully loadedposition'.

It is known that inany car a spring deflection of 41/2 inches (measuredas the amount by which the suspended massA approaches the road wheelcenters as the springs are compressed from their free position to thatposition assumed under normal full load) is the very least which can bevused if the frequency is not to exceed cycles per minute. /f/

In any car, and irrespective of its size dr weight, the springdeflection should therefore not be less than 41/2 inches and only byusing a suspension of not less than this deflection can objectionable55l cerned.

higher frequency oscillations be avoided. This .is at once a departurefrom standard present day practice as far as the front suspension iscon- The actual ride is affected not only by'thefrequency, but also bythe actionor type of oscillation which depends on the position of thetransverse axes of oscillation. Y

The actual oscillations of an automobile are usually compounded of pitcwhich may be defined as an oscillationabout a vvirtual axis alwayswithin the wheelbase, and bounce which may be dened as an oscillationabout a virtual Y axis in frontof or behind the automobile.

'Ihe farther these axes are removed from the axles, the more nearly is aso-called fiat ride attained-the vehicle body moving vertically underroad shocks while maintaining a position' substantially parallel to theground. Such a fiat ride is free from the violent pitching or rockingmotion which is so noticeable in conventional cars where theoscillations'about the pitch axis located in the space between the twovwheel axes and about the bounce axis located only Ya. small distance infront Vof the front wheels, have ai large horizontal force componentwhich jerks the neckmuscles of the passengers.

The fundamental relationship requirement for simple harmonic motion ofa'body about ferent transverse axes is that E Y should equal unity wherek is the polar radius two difoi' gyration of the mass of the body aboutits center of gravity and a andb are the ldistances of the respectiveaxes from the transverse vertical plane containing the center ofgravity, and that at the same time the deflections of the supportingsprings at either end of the body should be equal. Expressed otherwise,this means -that when one axis is thecenter of percussion the other axisis the center of `rotation orangular oscillation; or that any verticalblow in the plane of one axis will be without influence on theposition-of the body at the plane of the other axis.

Considering now a'mass tofbe suspended on springs towards either end,the springs at each end being deflected an Y equal amount by themasses,the bounce axis will Vbe at iniinity and the pitch axis inthevertical plane of the center of gravity.

It might appear that an automobile Yshould have a ratio equal to unitywith equal spring deflection front and rear since, when equals unity andthe front and rear spring defiections are equal, the frequencies inpitch and bounce are equal, and these are the only conditions inwhichthe frequencies are equal. desirable that the frequencies of pitchand bounce shouldV be reasonably close together since, to the extentthat'they are dissimilar, there maybe very objectional interferenceforheterodyne ei'- fects between the 'oscillations of the pitch; and

bounce, producing sudden augmented impulses.

highly Yobjectionable to the passengers. When in an automobile the ratio1 approaches unity, the oscillating axes'approachy the vertical planesof the axles; when so located It is '65: ItY can be shown that thesquare oi' the bounce' neither of them are true pitch or bounce axes asdefined abovesince they are neither within nor without the axles orWheelbase.

On the other hand, when the front and rearA spring deflections are equalthe bounce axis tends to be at infinity and the pitch axis in thevertical plane containing the center of gravity whatever the value ofmay be.

'I'he two conditions in combination are conicting, and as a result thepositions of the oscillatingV axes are indeterminate, the behavior Ithas been found that this is indeed the case and that by reducing theratio the frequencies in pitch and bounce arel still so close that nodistinct interference kicks occur while, however, the car has morenearly definite oscillation centers with a characteristic anddeterminate action 1 If now, S1=front spring stiffness in lbs. per inchdeiiection rea` spring stiffness in lbs.- per inch deiiecton Y w1=pitchfrequency in radians per second wz=bounce frequency in radians persecond M=mass ofthe vehicle a :distance of front spring from verticalplane of lcenter of gravity Y b :distance of rear spring from verticalplane of center of gravity then with equal spring deflection front andrear With equal spring deflections front and rear, the bounce axis is atinfinity and the pitch axis in the vertical plane of the center ofgravity. `The bouncing consists of pure linear oscillations,l and thepitching consists ofpure rotary oscillations.

u1.013 A Sri-S3 dividing numerator and denominator by Si 1.12-1 er) 1wfg-k2 (12+ S1 X S2 1+-S- l but .w1 1 au 1 "wz-k2 1H-) 1+.S-2 a 1a 1S2b2 a 1 E 62+ Sib 1+S2Xl1 z a -Ic-zab l a 1+ aLl-ab (IZ a k2 and ya*Pitch frequency c b wig-Bounce frequency It2 Thus with l k2 i Et equalto .8 and equal spring deflection front and rear, the ratio pitchfrequency 1- g rear spring deection front spring deflection equal tounity with virtual pitchv axis at the i" center of gravity and virtualbounce axis at innity, can with advantage be departed from to eiect achange, in the position of the oscillating centers towards increasedactual comfort.

The virtual pitch axis will always,y lie between 1 motion, tov acombination of bounce (a motion ywhich,-while not a parallel motion, isstill about an axi's some distance away from the car) and a pitchingmotion which is more nearly parallel y or up and down, thus improvingvthe combined effect towards an actual flatter or parallel combinedmotion, with a normal load.

If, in an actual car with the center of gravity approximately centralthe passengers are grouped towards the rear axle, the axiscf pitch canbe brought towards the front axle away from the rcenter of gravity byVincreasing the deflection of the front springs, and it has been foundthat a ratio of rear spring deflection Y front spring deflection equa1to :i5 at light load up to 1.o 'at maximum load gives probably thegreatest over-all improvement.

a transverse Vertical plane containing the centerv of gravity and thatroad wheel axis which has l the greater spring deflection, while thevirtual bounce axis will be on that side of the transversevertical planecontaining the center of gravity away from the pitch axis. The virtualbounce axis moves from infinity towards one axle as thev rear springdeflection front spring deflection y departs from unity. Since, however,the ratio rear spring defiection front spring deflection willy vary withthe variable live load consisting,

ofl passengers and fuel load (vv ich may be a considerable percentage ofthe total load), then in a car in which the passengers are grouped forthe A still further advantage results from the use of a greater `frontspringk dellection, in that a force applied as by a bump to the frontwheels will have a greater moment about the bounce axis than about thepitch axis. For this reason the initial movement will be practicallypure bounce and the rear of the car will be lifted, thus softening theimpact which is to follow as the rear wheels pass o'ver the bump andalso preparing the rear springs to receive this impact.

While in the foregoing it= was assumed that the center of gravity of thesuspended mass could be anywhere within the wheel base and it was onlynecessary that the masses should be so disposed as to have the requiredpolar moment about a horizontal transverse axis through the center ofgravity, the position of the centerY of gravity of the suspended massinfluences the roadability and stability of the automobile considerablyand a. position approximately 'midway between front and rear axles isvery necessary for stability on cambered roads and when cornering. Thisdisposition is desirable also for equal division of the load between thewheels and, in any case, a forw'ard center of gravity is likely to bringparking and traction dicultiesfwhile a rearward center of gravity isaccompanied by skidding on turns.

It has been found best to obtain xed and determinate centers ofoscillation byi making'the ratio /f\ less4 than unity rather thangreater than unity because with the'y desired central position of the y,center of gravity relative to thev axles there would /have to be a massconcentration to the outside of the axles forl being a practicaldifliculty in obtaining such a.

most part to one side of a transverse vertical mass disposition of theessential parts of the car,

to be greater than unity; andin addition to there there is still anotherreason which makes a higher value of undesirable, since it would meanincreasing the moment oi' inertia of the suspended mass of the car abouta vertical as well as a transverse axis through the center of gravityand this would make the car harder to turn as well as increasing theprobability of skid on entering a turn.

'I'he comparison between a conventional car and a car built according tothe invention is as v follows:

In the conventional car the ratio E ab equals about .6, the ratio rearspring deflection front spring'deliection is greater than 1 andfrequently '2 or 3 with an actual spring deflection of the front springsoi less than 4 inches, and the center of gravity is approximatelycentral. The result of these re-4 to the dissimilar frequencies of thecomponentl oscillations with resonance at some times greatly increasingtheir amplitude; the pitching oscillation about a center below thepassengers has a large horizontal component which jerks the passengersneck muscles; and. the proximity of the bounce axis to the front axlemeans that vertical blows at the front wheels produce a motion almostthesame as that about the pitch axis. The

vpassengers are more or less violently disturbed.

In a car built according to the invention, the ratio f Y k, E

equals about .8, the ratio rear spring deflection 93 front springdeflection with an/average spring deilection of 7 inches, and the centerof gravity approximately central. The result of these relationships isthat the oscillationsare of a comfortable and closely similar frequency(the ratio pitch vfrequency to bounce frequency' being approximately as5 is to 6), the pitch center is forward of the center of gravity (awayfrom the passengers who are grouped to the rear), and the bounce centeris some distance to the rear of the vehicle. A distinct improvement inthe action of the car is effected, a flatter" ride is obtained withelimination of interference kicks," the passengers are not jerkedforward but are oscillated gently up and down at a comfortable frequencyand are least discomilted by such an arrangement ofthe ratios of thefactors involved and their relationactual "roadability or ease ofhandling with safety at all speeds has been improved.

'I'he accompanying drawings show one way in which the required.disposition of the parts and the masses is obtained in an actualautomobile.

In the .drawings Figure l is a side elevation of an automobile builtaccording to the invention and showing the disposition of the principalmasses in dotted lines.

Figure 2 is a plan view of the chassis.

Figure 3 is an enlarged, partly broken away, part-sectional view in thedirection of the arrow I of Figure 2 showing the way in which the frontsteering wheels are supported from the chassis.

Figure 4 is an enlarged section on the line 4-4 of Figure 2.

Figure 5 is an enlarged, partly broken away, part-sectional view on lineB-I of Figure 2.

The engine I is mounted farther forward -in relation v'to the front axleand the car as a whole than is usual, and since such a forwarddisposition would interfere with the up and down movement of theordinary front axle under spring deilection if the distance between theaxle and the under side of the engine were not increased,

it has been found convenient to adopt. independent front wheelsuspension. There is a further advantage in the adoption of independentsuspension in that it readilyfpermits of the use of the desired softerfront springs. The use of independent suspension also increases theeiIective sprung masses at the ends of the car, thus increasing themoment of inertia of the sprung masses without necessarily increasingthe moment of inertia of the car as a whole.

'I'he battery 2 has been brought forward alongside the engine away fromthe usual position amidship of the car.

Since the requirements Aof the invention are concerned with the sprungmass, this has been increased at the rear by supporting the diilerentialhousing 3 on the frame.

Still further to increase the moment of inertia of the sprung masseswhile maintaining the approximately central center of gravity, the sparetires 4 and S'with rims or wheels are carried in a boot 6 which is in anextension of the body to the rear of the frame. Also in the boot are twogasoline tanks 'l and 8,one on each side of the spare tires. A trunk 9and tool box I0 are similarly carried in the boot on shelves II and I2.

The resultof the foregoing distribution of the sprung masses is a massconcentration on each side of the center of gravity which is representedin FigureV l by the two spheres Wi and W2. In this ligure, k representsthe radius of gyration o! these masses from the center of gravity G. aand b are the horizontal distances of the front and rear axlesrespectively from the transverse vertical plane of the center ofgravity. The masses W1 and W2 have been represented as of unequalamount, unequal distances k1 andkz, respectively away from the center ofgravity. It will be appreciated that they might be similar and hence asimilar distance from the center of gravity. In any case, Ic representstheir mean` distance from the center of gravity.

The frame is narrow and the side members I3 and I3' are parallel andsubstantially straight, providing a frame of high torsional rigiditywith a low weight. Cross members I4, I5, I6, I1, 4I, and 5i!V connectthe side members.` The membersr I6 and I'I form an X-member.

ship toone another, while at the same time the Each front wheel I 8 orIl is supported vby a pair of swinging V-shaped supporting members orstructures having two arms I9, 20 and 2|, 22 respectively, pivoted tothe chassis frame at points 23, 24 andv25, 26 respectively, and withlink pins 21 and 28 at their apices carrying a king pin bracket piece 29on which the wheel spindle 29' is pivotally supported.

The axes through 23, 24 and 25, 26 and the axes of the link pins 2l and28 are all parallel to one another in their respective wheel lsupportingsystems at an angle to the longitudinal axis ofthe frame divergingoutwards towards the front end thereof. In addition, the forward ends ofall the axes are tilted upwards away from the horizontal so that theaxes lie in planes at right angles tothe king pin 29 which is arrangedto have the usual small "caster angle as a result of which the front'wheels are given a tendency to maintain themselves in a straight aheadposition.

-The upper member I9, 20 is considerably shorterthan the lower member2I, 22. As a result, when these members swing about their pivots thetrack of the tires remains constant and the portion of the tire incontact with the road is not subjected to side thrusts or any scrubbingaction. Y

A plate 30 is secured between the arms 2| and 22 of the lower wheelsupporting member in such away that the three together form a letter A,constituting a strong and rigid assembly well able to resist forcesAparallel to the ground occurring during the operation of the vehicle.

The plate is formed to serve as a seat fora coil spring 3I whichsupports the frame, the upper end of the spring bearing on a bracket '32y xed to the frame.

The spring reaction against the bracket 32 serves to clamp a `cup shapedmember 33 to the bracket, the member 33 serving as a stop to limit thedeflection of spring 3l. A rubber cushion 34 is attached to plate 30 tosoften the blow.

'Ihe location of the plate 30 about three fifths of the distance fromthe axis 25, 26 to the pvot 28 permits the use of a very practicaldesign of coil spring having such relative dimensions of wire diameter,coil diameter and operating length as to give a stable spring under itsusual working deflection while at the same time permitting an extremelysoft front suspension. The stiffness of the suspension at the frontwheel will be (i3/5) 2 or .36 of the spring stiffness.

The rear wheels 35 and 35 are mounted on bearings in turn supported 'byhollow hubs integral with lever arms 36 which havefhollow hubs 3lsupported on bearingsl on transverse tubular shafts 38 which are locatedforward of the wheels. The diiferential housing 3 has attached to it atubular cross shaped member 39 to which also are attached the tubularshafts 38. These tubular shafts 38 are mounted in rubber bushings 40supported in bearings 4I through the frame-side sembly constitutes alsoa strong cross member on which the arms 36 are pivoted. In this way roadshocks received by the rear wheels and also gear vibrations arising inthe differential housing' are resiliently cushioned from the frame bythe rubber mountings.

Semi-cantilever leaf springs 45 are mounted on spring perches on thehubs 3l of lever arms 36. These leaf springs extend rearwards beyond therear wheels and have their outer ends shackled to brackets on the rearcross member I9.

The mounting of the pivot points for the arms 36 for the'rear roadwheels forward of the wheels causes a tendency for the rear end of thechassis to be depressed by braking reaction when the brakes are applied.Any such depression is in opposition to the tendency of a vehicle topitch or rock forward about a horizontal transverse axis when the brakesare applied. This latter tendency is more pronounced when the softerfront springs necessary for a good ride are adopted and hence thegreater desirability for the tendency towards depression of the rear endunder braking reaction in a ,car built'accordlng to the invention. Y

The drive from the diierential housing to the rear wheels is takenthrough universal andvtelescopic joints by the drive shafts 46.

Mounted in the longitudinal branches of the tubular cross shaped member39 is a drive shaft for the pinion of the ring gear in the differentialn steering arms are connected to the steering lever by a pair/ of tierods 53,y having ball and. socket joint connections with the steeringarms and the steering lever at 54. The tie lrods 53 are pivoted to thesteering lever at points whic in the nor.

' mal position of the parts are substantially in alignment with thepivot axes 25, 26 of each wheel supporting means so that the steeringarrangement will be substantially unaffected by rising and fallingmovements of the wheels.

I claim: f

In a power driven vehicle the combination comprising a frame, a vehiclewheel, a wheel carrier/a pair of links forffconnecting the wheel carrierto the frame pivotally connected at one end to said frame one above theother so as to be capable of swinging only in a vertical plane aboutparallel axes xed with respect to the frame but incapable of movementrelatively to the frame in any other direction, said links beingpivotally connected to the wheel carrier to form with the wheel carrierand the frame an articulated quadrilateral, and a frictionlesshelicalcompression y spring interposed between one of said links and the frameso as to oppose the vertical swinging motion of the links, said springbeing freely movable laterally substantially over its entire length andbeing secured against lateral displacement at its ends with respect tothe frame and' th link, respectively. MAURICE OLLEY.

